The invention relates to pliers.
Such pliers are already known from WO 95/23048. These known pliers contain a first operating jaw and a first plier handle fixed thereto, a second operating jaw which is mounted pivotably on the first operating jaw by means of a pivot pin and forms a plier mouth with the first operating jaw, a second handle which is mounted pivotably on that section of the second operating jaw which is oriented towards the rear plier end, and a resilient connecting element, of which one end is provided on the second plier handle, just behind the second operating jaw, and the other end is provided on the first plier handle.
In the case of these pliers, the connecting element serves for improving the elasticity of the pliers.
Further pliers of the type mentioned are known from DE 31 09 289 C2. In this case, a spring element is arranged in a force-transmission path such that the pliers give a smooth, comfortable actuation feel. The spring element may have, for example, V-shaped steel spring arms and be located between a pivot pin of one of the operating jaws and the other operating jaw, which has a slot for accommodating the pivot pin.
The object of the invention is to develop pliers of the type mentioned in the introduction such that better results can be achieved when working with them. In particular, it is intended to be possible to allow better self-adjustment of the force behaviour in the plier mouth in dependence on the closing movement of the operating jaws, to be precise also in relation to different sizes of objects which are to be processed in the plier mouth.
The solution of the set object consists in that the pivot pin is fastened on one of the operating jaws, and located in the other operating jaw is a slot for accommodating the pivot pin, the longitudinal direction of said slot running in the plier plane, at least more or less perpendicularly to the longitudinal direction of the pliers, and in that a tension spring has one end fastened on the pivot pin and its other end fastened on the operating jaw which has the slot.
The combination of tension spring and resilient connecting element makes it possible, according to the invention, for the force behaviour in the plier mouth to be adapted very precisely, in dependence on the closing movement of the operating jaws, to desired conditions, even for the case where objects of different sizes are to be processed in the plier mouth, with the result that better results may thus be achieved when working with the pliers. This applies, in particular, when the pliers constitute a crimping tool by means of which it is intended to press, for example, wire end ferrules or other contact elements onto ends of wires. The force behaviour in the plier mouth, in dependence on the closing movement of the operating jaws, is adjusted in that the respective spring characteristics of the tension spring and connecting element are combined with one another.
In this case, for the purpose of producing a desired force behaviour in the plier mouth, it is possible for the tension spring and the connecting element to be designed such that, over a closing displacement of the operating jaws which is limited by the length of the slot, the necessary mouth force is applied by the tension spring and the connecting element and, over a following closing displacement of the operating jaws, said force is provided solely by the connecting element.
Such a configuration is possible if the tension spring, which is otherwise used for the precise adjustment of the mouth force, would be over-extended in the case of the mouth forces being too large or the closing displacements of the operating jaws being too long. In this case, the tension spring is disengaged and the necessary mouth force is then applied, over a further closing displacement of the operating jaws, solely by the connecting element. This makes it possible to ensure, even over relatively large closing displacements of the operating jaws, the production of a desired force behaviour in the plier mouth.
According to one configuration of the invention, the spring characteristics of the tension spring and connecting element may be adapted to one another such that, once the closing displacement of the operating jaws which is limited by the length of the slot and further closing movement have been achieved, the smoothest possible force behaviour in the plier mouth is obtained.
This makes it possible to carry out a more uniform deformation operation in the plier mouth and thus to achieve an even better result when working with the pliers. This measure allows particularly favourable ergonomic handling of the pliers.
In one configuration of the invention, the connecting element may be designed such that it yields to a pronounced extent once it has exceeded a predetermined plier-mouth limit force. This avoids, during further closure of the plier handles, damage, in particular, to relatively large parts which are to be processed in the plier mouth, and it is made possible for a catch, which usually interacts with the pliers, to be disengaged from a row of teeth in order for it to be possible for the plier mouth to be opened.
In yet a further configuration of the invention, the pivot pin is preferably fastened on the second operating jaw, the slot being located in the first operating jaw. This makes it possible for the tension spring to be fastened on the first, non-movable operating jaw, with the result that it is not pivoted during operation of the pliers and its characteristic thus cannot be distorted.
The tension spring itself may be of any suitable form, but preferably it may also be designed, for example, as a V-shaped, U-shaped or xcexa9-shaped leaf spring. With springs of this type, the desired characteristic can be set particularly easily by selection of the appropriate dimensions and/or material thicknesses.
The connecting element used may preferably be a flat-plate-like spring plate or an assembly of such spring plates, it also being possible with these plates for the spring characteristic to be easily predetermined by appropriate material dimensions and material thicknesses.